1. Field of the Invention
This invention relates to a laminated organic photosentive material which has a charge producing layer and a charge transporting layer formed on an electroconductive support and which has in particular a high sensitivity to a semiconductor laser region wavelength so as to be suitable for use as a photosentive material for a laser beam printer.
2. Description of the Prior Art
A composite or laminated type organic photosensitive material has been developed and put to practical use in recent years. This type of organic photosensitive material is disclosed in, for example, Japanese Patent Publications Nos. 42380/1980 and 34099/1985. It comprises an electroconductive support, and a charge producing layer and a charge transporting layer formed on the support. For instance, such a composite photosensitive material has an electroconductive support 1 of aluminum layer 2 deposited on a polyester film 3, a charge producing layer 4 formed on the aluminum layer, and a charge transporting layer 5 formed on the charge producing layer, as illustrated in FIG. 2.
The charge producing layer is formed by, for example, preparing a dispersion of a charge producing substance together with an organic solvent, a binder resin, and if necessary a plasticizer, applying the dispersion onto the support, and drying to a thin film. The charge transporting layer is formed by, for example, dissolving a charge transporting substance in an organic solvent together with a binder resin, and if required a plasticizer, applying the solution onto the charge producing layer, and drying to a thin film. A charge transporting layer may be first formed on the support, and then a charge producing layer on the charge transporting layer.
There are already known a number of laminated type organic photosensitive materials containing a variety of charge producing substances and charge transporting substances in the charge producing layer and charge transporting layer, respectively. For example, there is described in Japanese Patent Laid-Open No. 60-255854, a photosensitive material which contains a hydrazone compound represented by the formula: ##STR2## as a charge transporting substance, and a metal phthalocyanine compound such as copper phthalocyanine or a nonmetal phthalocyanine such as tetramethylphthalocyanine or dialkylaminophthalocyanine as a charge producing substance. However, these known photosensitive materials are still unsatisfactory in charging properties or sensitivity.
As above set forth, it is already known that a metal phthalocyanine and a nonmetal phthalocyanine are photoconductive, and in particular, a single layer photosensitive material which employs the X-type nonmetal phthalocyanine as a photoconductive material is disclosed in U.S. Pat. No. 3,816,118. However, this known photosensitive material has a very low sensitivity.
Meanwhile, there has been a demand for a laminated organic photosensitive material for use in a laser beam printer which is sensitive to a long wavelength region from about 750 nm to about 850 nm, and for such a purpose the use of a variety of charge producing substances and charge transporting substances have hitherto been proposed. However, any of these known laminated organic photosensitive materials which employ the beforementioned specific hydrazone compound as a charge transporting substance has a low sensitivity to a semiconductor laser region long wavelength from about 750 nm to about 850 nm.